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Details of Grant 

EPSRC Reference: GR/A00522/01
Principal Investigator: Mulholland, Professor AJ
Other Investigators:
Researcher Co-Investigators:
Project Partners:
Department: Chemistry
Organisation: University of Bristol
Scheme: Advanced Fellowship (Pre-FEC)
Starts: 01 April 2000 Ends: 30 September 2003 Value (£): 104,794
EPSRC Research Topic Classifications:
Catalysis & enzymology Chemical Biology
Chemical Structure
EPSRC Industrial Sector Classifications:
Chemicals Environment
Related Grants:
Panel History:  
Summary on Grant Application Form
Simulations are a useful approach to the study of enzyme-catalysed reaction mechanisms, the dynamics of enzyme-substrate complexes and processes of conformational change associated with reaction. Simulations complement experimental investigations, and can provide information which is otherwise difficult to obtain, such as on unstable intermediates and transition states, and allow contributions to catalysis to be quantified. It is proposed to examine two enzymes, citrate synthase and aspartate B-semialdehyde dehydrogenase (ASADH), by simulation techniques. These studies will elucidate details of the catalytic mechanisms which remain somewhat uncertain. The techniques to be used include molecular dynamics simulations, algorithms for determining pathways of structural change in macromolecular systems, and quantum chemical and combined quantum mechanical/molecular mechanical modelling of the reactive processes in the enzymes. For ASADH, the simulations will be carried out in conjunction with time-resolved crystallographic investigations of the enzyme reaction, and other structural studies. The calculations will provide indications of how the enzyme modulates the intrinsic reactivity of the substrate, cofactor and catalytic residues to achieve its rate acceleration, and the relationship of chemical changes to observed conformational changes. In addition, they will assist in the process of crystallographic refinement of reaction intermediate structures by providing models incorporating dynamic and structural variability. For citrate synthase, the focus will be on comparing the enzyme from organisms adapted to high temperatures (thermophiles) with those from more normal environments. Thermophilic enzymes are more stable then their mesophilic counterparts, but typically exhibit reduced activity at room temperature, despite high structural similarity. Examination of the dynamic and conformational behaviour of thermophilic and mesophilic citrate synthases will provide insight into the causes of differences in activity and stability. The chemical mechanism, and the stabilization of intermediates, will be investigated along with the change from an open to a closed form which accompanies the reaction. This work will be performed in collaboration with experimental research on the structure and kinetics of extremophilic citrate synthases. Analyses of the type proposed here should give more detailed understanding of the nature of enzyme action, with important implications for the development of efficient, stable catalysts with designed activities.
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Organisation Website: http://www.bris.ac.uk